A knife-wielding man hijacked a bus on Monday in rural Norway and killed the driver and two passengers before he was detained by authorities, officials said.

Police in Sogn and Fjordane county in western Norway gave few details about the suspect, but described him as a local resident originally from South Sudan. Police attorney Trine Erdal said the suspect was in his early 30s, not in his 50s as police had earlier reported.

The motive for the killings was not immediately clear.

The victims were two men in their 50s – the Norwegian bus driver and a Swedish passenger – and a 19-year-old Norwegian woman, Erdal said. All had been stabbed. There were no other passengers on the bus, she added.

The suspect was initially apprehended by rescuers from the fire department who were the first to arrive on what they thought was an accident scene, police said. The suspect was later arrested by police and taken to a hospital for treatment of cuts but was not seriously injured, Norwegian news agency NTB reported.

Oslo police said they called off the deployment of an anti-terror unit after receiving reports that the suspect had been arrested.

The same bus route was attacked in 2003 when an Ethiopian man stabbed to death a bus driver, NTB said. He had earlier that day killed a Congolese asylum seeker at a refugee centre.

Multiple killings are rare in Norway, though the country was shocked by its worst peacetime massacre two years ago when Anders Behring Breivik, a Norwegian rightwing extremist, killed 77 people in a bomb and gun rampage.